This invention relates to antennas for citizen band operation and more particularly to top-loaded, helically-wound vertical antennas for citizen band transmitters and receivers.
The antenna structure of this invention is adapted to mobile transmitter-receiver installations such as would be utilized for land or water mobile vehicles. In installations of this type, the antennas of prior art constructions generally comprise a single, electrically conductive element that is fed at one end and is effective as both a receiver and radiator of electromagnetic wave energy in a radio frequency spectrum. Such antennas have a physical construction to accommodate the mechanical force that may be applied to the antenna by the movement of the vehicle. Such antennas are generally constructed of metallic tubing having an electrical length equal to a quarter-wave in length of the desired communication frequency. These range in physical length from about nine feet for 27 mc to about 6 inches for 470 mc. The antennas are vertically mounted and supported at the bottom where they are end-fed.
It is well known that an electrical quarter-wave antenna may be physically shortened and still be effective as the desired wave length of adding inductances in series.
One of the major problems encountered in the construction of top-loaded, helically-wound citizen band antennas is that the operator will temporarily apply considerably greater energy to the antenna than is recommended. Citizen band antennas are generally designed to accommodate a 5 watt transmitter-receiver. Consequently the top-loaded coil is frequently burned out because of the temporary overloading. Frequently the very end of the antenna will produce a corona effect which ionizes the air around the very top end of the antenna causing damage to the antenna. Additionally, it has been found that such top-loaded antennas are particularly sensitive to atmospheric static.
One of the principal objects of this invention is to provide a simple top-loaded, helically-wound vertical antenna for citizen band operation that is a very efficient antenna and is capable of withstanding temporary overloading.
An additional object of this invention is to provide a top-loaded, helically-wound vertical antenna that reduces the static received at the designed frequency.
A further object of this invention is to provide a top-loaded, helically-wound, vertical antenna that has an extended distance range of communication over other prior antennas.
An additional object of this invention is to provide a top-loaded, helically-wound, vertical antenna for citizen band operation that has an increased reception distance range.
These and other objects and advantages of this invention will become apparent upon reading the following detailed description of a preferred embodiment.